Anti-scaling and anti-corrosive study on waterborne composite coatings based on siloxane-g-polybutadiene incorporated with PTFE and nano-SiO2-EDTA

SiO2-EDTA composite particles are prepared by using nano-silicon dioxide (SiO2) as the loading particle and ethylenediaminetetraacetic acid (EDTA) as the scaling inhibitor. Then, SiO2-EDTA particle and polytetrafluoroethylene (PTFE) micro powder are added in water-based silanized maleic anhydride-g-poly(1,2-butadiene) (SiMLPB) to fabricate composite coatings with good anti-scaling and anti-corrosion properties. The water contact angles (WCA) of SiMLPB increase to a maximum of 103 degrees with the addition of PTFE at 3 wt% and then decrease slowly; based on this formulae, the WCA improves to 109o when SiO2-EDTA is added up to 2 wt%. SiMLPB/PTFE coatings exhibit good corrosion resistance with the addition of PTFE; the SiMLPB/3%PTFE/2%SiO2-EDTA composite coating possesses impedance (|Z|0.01Hz) value at 2 orders higher than that of the SiMLPB/PTFE0 coating at low frequency, suggesting the much greater improvement in corrosion resistance due to the synergistic effects of adding nanoparticle as a surface modifier and EDTA as a corrosion inhibitor. The deposition of CaCO3 on this SiMLPB/PTFE/SiO2-EDTA composite coating reaches 0.0132 g/cm2 after 120 h scaling test, which is about 79% lower than that on the pure SiMLPB coating, resulting from the chelation of EDTA that promotes the formation of more unstable scales. The improvements in both anti-corrosion and anti-scaling performances are attributed to the hydrophobic function of PTFE and nanoparticle as well as the dual functions of EDTA at an appropriate addition of SiO2-EDTA.